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Research Papers: Flows in Complex Systems

Measured Static and Rotordynamic Characteristics of a Smooth-Stator/Grooved-Rotor Liquid Annular Seal

[+] Author and Article Information
J. Alex Moreland

Turbomachinery Laboratory,
Texas A&M University,
College Station, TX 77843
e-mail: morelandjames9292@gmail.com

Dara W. Childs

Professor
Mechanical Engineering,
Texas A&M University,
College Station, TX 77843
e-mail: dchilds@tamu.edu

Joshua T. Bullock

Valero Energy Corporation,
Port Arthur, TX 77640
e-mail: joshuatbullock@gmail.com

Contributed by the Fluids Engineering Division of ASME for publication in the JOURNAL OF FLUIDS ENGINEERING. Manuscript received November 1, 2017; final manuscript received June 27, 2018; published online August 6, 2018. Assoc. Editor: Bart van Esch.

J. Fluids Eng 140(10), 101109 (Aug 06, 2018) (9 pages) Paper No: FE-17-1711; doi: 10.1115/1.4040762 History: Received November 01, 2017; Revised June 27, 2018

Electric submersible pumps (ESPs) utilize grooved-rotor/smooth-stator (SS/GR) seals to reduce leakage and break up contaminants within the pumped fluid. Additionally, due to their decreased surface area (when compared to a smooth seal), grooved seals decrease the chance of seizure in the case of rotor-stator rubs. Despite their use in industry, the literature does not contain rotordynamic measurements for smooth-stator/circumferentially grooved-rotor liquid annular seals. This paper presents test results consisting of leakage measurements and rotordynamic coefficients for a SS/GR liquid annular sdeal. Both static and dynamic variables are investigated for various imposed preswirl ratios (PSRs), static eccentricity ratios (0–0.8), axial pressure drops (2–8 bars), and running speeds (2–8 krpm). The seals' static and dynamic features are compared to those of a smooth seal with the same length, diameter, and minimum radial clearance. Results show that the grooves reduce leakage at lower speeds (less than 5 krpm) and higher axial pressure drops, but does little at higher speeds. The grooved seal's direct stiffness is generally negative, which would be detrimental to pump rotordynamics. As expected, increasing preswirl increases the magnitude of cross-coupled stiffness and increases the whirl frequency ratio (WFR). When compared to the smooth seal, the grooved seal has smaller effective damping coefficients, indicative of poorer stability characteristics.

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References

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Figures

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Fig. 1

Detailed drawing of rotor grooves (dimensions in mm)

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Fig. 2

Cross section view of the main test section

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Fig. 3

Cross section view of the stator assembly and rotor. The solid arrows denote inlet flow paths while dashed arrows denote outlet flow paths.

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Fig. 4

Comparison between SS/GR and SS/SR seals. Q˙ versus ΔP at ω = 2 and 8 krpm for ε0 = 0.00.

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Fig. 5

Cross section view of (a) radial injection (low PSR), (b) tangential injection (medium PSR), and (c) tangential injection (high PSR) inserts (dimensions in mm)

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Fig. 6

(a) Axial and (b) radial position of the Pitot tubes (dimensions in mm)

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Fig. 7

Outlet swirl ratio versus PSR at ω = 2 and 6 krpm for ε0 = 0.00

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Fig. 8

(a) Non-drive-end view of the rig coordinate system, (b) definition of position in the rig coordinate system, and (c) presented coordinate system

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Fig. 9

View of the stator assembly, instrumentation, and coordinate axes from the nondrive end

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Fig. 10

Grooved-rotor/smooth-stator seal KXX and KYY versus ε0 at ΔP = 6.21 bar

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Fig. 11

Comparison between SS/GR and SS/SR seals. Stiffness versus ε0 at ω = 4 krpm, ΔP = 8.27 bar.

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Fig. 12

Comparison between SS/GR and SS/SR seals. Stiffness versus PSR at ω = 2 krpm, ΔP = 4.14 bar, and ε0 = 0.00.

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Fig. 13

Comparison between SS/GR and SS/SR seals. Damping versus ε0 at ω = 4 krpm, ΔP = 8.27 bar.

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Fig. 14

Comparison between SS/GR and SS/SR seals. Virtual mass versus ε0 at ω = 4 krpm, ΔP = 8.27 bar.

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Fig. 15

Grooved-rotor/smooth-stator seal WFR versus PSR for ε0 = 0.00 at ω = 2 and 8 krpm

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Fig. 16

Comparison of SS/GR and SS/SR. Ceff versus ΔP at ε0 = 0.00.

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Fig. 17

Stator assembly inlet and outlet chamber dimensions (mm)

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Fig. 18

Back-pressure labyrinth-tooth seal dimensions (mm)

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